Originally Posted By: PandaBear
Makes you wonder why we have so much water on earth but not much in mars when both are so similar.
I believe I can answer that. Once upon a time, both earth and mars were much, much hotter than they are today. Earth was nothing but a rock of molten lava, cooling slowly. Today, we still retain much of that heat, because we are much closer to the sun than mars, and because earth is much larger. This means that our core still retains much of the heat of planet formation, and is active, providing us with plate tectonics, and a magnetosphere.
Mars is much further away, and much smaller than earth. It is theorized that once upon a time, Mars was very much like earth is today. Warmer, with a real atmosphere similar to the early earths atmosphere- likely a reducing atmosphere. It was covered with liquid water, the giant chasms on the surface are identical to those on earth, formed when giant glaciers melted, and ice dams collapsed, with trillions of gallons of water suddenly flooding onto plains, carving out canyons. Only much, much larger.
We know mars was an active world once, because of this. And because it has volcanoes, Olympus Mons for example, the largest volcano in our solar system, makes Mount everest look almost like an anthill. But because it is further away, and smaller, Mars core lost it's heat much more quickly than the earth did, freezing solid. With no active core driving a magnetosphere, the solar wind blew Mars' atmosphere into space, leaving behind a trace atmosphere of Carbon dioxide, at such a low pressure that on the surface, you're blood would boil in the relatively mild temperatures. Mars surface can be extremely cold, but it can be liveable for humans in some areas, warmer than negative 100 fahrenheit. With no atmosphere left, the oceans boiled away into space, leaving behind a dry surface. It appears that some water may still be trapped deep in the martian soil.
